This invention relates to an improved method for the treatment of inorganic materials. In particular, the invention relates to the treatment of natural stones. Over the years many different methods for treating natural stones, have been proposed. Stone surfaces were polished by the standard mechanical method and various sealers applied. No sealer was truly effective because the sealers could not penetrate the pores of the solids and thus they did not form a good bond. The penetration of these sealers were not efficient and had to be constantly reapplied. Consequently, over the years some stones suffer serious decay due to exposure to atmospheric chemical reaction. Water vapor in conjunction with carbon dioxide, hydrogen oxide, hydrogen sulfide, sulphur dioxide, citric acid, hydrochloric acid, etc., attack the natural stone surface. The results of this attack on the surface lead to intrinsic deterioration of the stones and items made out of these stones, such as statues, table tops, vanities, marble sinks, registration desk tops, etc.
Recently various methods for treating inorganic porous solids have been disclosed in patents which are based on the concept of preventing the decay of natural stones. For example, in Price, U.S. Pat. No. 4,478,911, treatment of a porous inorganic material is suggested using a single phase liquid mixture comprising alkoxysilane, water, organic solvent and a sylanol polymerization catalyst. While somewhat effective for materials having large pore size, it is ineffective for low porosity materials such as marble in which a high viscosity media such as the liquid mixture mentioned in this patent tends to diffuse outwardly during curing, especially in the smallest pores of the solid. Therefore, it is desirable to render a method for deeply impregnating such low porosity material which is not dependent upon the viscosity of the mixture to force penetration. Another method for treating inorganic porous solids using an impregnating sealer has been suggested in Stiegler, U.S. Pat. No. 4,620,989, which describes a method of impregnating the surface of a stone with an acrylic based resin dispersion to seal off the pores of the stone. The dispersion is force-dried using dry air in a drying system which is intended to push the resin deeper into the pores. While somewhat satisfactory for highly porous materials such as sandstone, this method does not work for solids of low porosity, such as marble. The drawback of this method is that large amounts of the dispersion must be applied, a process which risks clogging up the pores of low porosity materials. An improvement on the method stated in U.S. Pat. No. 4,629,989, is the application of a dispersion that will not clog up the pores and which is allowed to penetrate without force drying in accordance with this present invention.
In a further suggestion for treating inorganic porous solids as shown in Gauri, U.S. Pat. No. 3,795,533, using a plurality of solvent mixtures, a sequence of solvent mixtures are applied to the surface of the solids. Each of the sequentially impregnated mixtures contains a higher concentration of curable polymeric material than the previously applied impregnated mixtures. The drawback of this method is that the pores being impregnated have not been sufficiently opened for the acceptance of the multilayered cure. Therefore the polymers suggested in this method may not be capable of deeply penetrating the pores of the solid.
Some of the known methods entail techniques for coating the surfaces of porous solids, particularly marble, and for the exclusion of moisture by applying water repellant surface sealants. However, it is believed that these prior art methods of treatment of natural inorganic solids have been inadequate because if sufficient drying does not occur, water trapped beneath the surface can cause further deterioration by absorbing gases such as CO.sub.2 and SO.sub.2. In contrast, the present invention comprises a method to prevent water from inhibiting polymerization or curing in resin and preventing contaminants from deteriorating the surface seal by using a chemical solution to force a regulated deep drying to occur prior to application of the sealant.